Many types of alloys are traditionally cast, such as those with applications in the transportation industries. Casting is a process in which a metal or a mixture of metals is heated until it is molten, then poured into a mold and allowed to cool and solidify. The as-produced microstructures of these cast products are generally large and non-uniform. Such microstructures lead to fast degradation and make the alloys unsuitable for biomedical implant applications. It would also be difficult for such implants to conform to regulatory protocols because they do not meet the criteria for GMP protocols for CE/FDA certifications.
In addition, casting frequently gives rise to defects such as segregations, precipitation shrinkage, micro- and macro-porosity, and inhomogeneous grain size and grain distribution during solidification. Such defects, which can sometimes be removed by post-processing methods, adversely affect the properties in at least two ways. First, the mechanical properties suffer due to the presence of defects. Second, inhomogeneous microstructure and the formation of intermetallic particles lead to an inhomogeneous degradation rate within the body. For these reasons, casting produces alloys that generally have defects which are undesirable in biomedical implants.
There is a need in the art for biodegradable magnesium alloys suitable for biomedical implant applications and having improved processability and mechanical properties such as strength, ductility, and strain hardening.